In an air conditioner for a vehicle described in PTL 1, an evaporator is arranged in an air conditioning case, and cools air to be blown into a vehicle cabin. In addition, a bypass passage is formed, through which air bypasses the evaporator. By forming the bypass passage, an air volume that passes through the evaporator can be reduced by an air volume that passes through the bypass passage. In this way, the air volume that passes through the evaporator to be cooled and the air volume that passes through the bypass passage not to be cooled can be adjusted in accordance with a requested temperature. Thus, drive power of a compressor can be saved by lowering the required cooling capacity of the evaporator.